1. Field of the Invention
The present invention relates to a technology for controlling power supply to a plurality of recording devices of a redundant-array-of-independent-disks (RAID) group.
2. Description of the Related Art
A power supply unit a device enclosure (DE) that includes a plurality of hard disk drives (HDDs), to supply power required to operate the HDDs. The power supply unit typically includes a protection circuit for a self shutdown when a malfunction occurs in the HDD (such as a short circuit or overcurrent). FIG. 3 is a schematic for illustrating HDDs that are stored in a conventional DE and power supply units. As shown in FIG. 3, a DE 10 includes HDDs 0 to n (n is a positive integer). Power supply units 20 and 30 supply power to each of the HDDs 0 to n. The HDDs 0 to n are linked to each other to compensate redundancy and constitute a RAID.
However, if a malfunction occurs in an HDD (for example, HDD 4) among the HDDs 0 to n, the power supply units 20 and 30 performs the self shutdown. In other words, as shown in FIG. 3, because a power supply system inside the DE 10 is common to all the HDDs 0 to n, power supply not only to the HDD 4 that is malfunctioning but also to other normal HDDs is cut off, thereby resulting in a shutdown of the entire DE 10 that includes other volumes of data. Particularly, in a small-scale RAID system that includes only the DE 10, the shutdown of the entire DE 10 results in immediate system shutdown and data loss, thereby affecting reliability.
To solve the above problem, a method has been proposed in which a power-off circuit that blocks power is provided in each slot (entry point of the HDD) of the DE. FIG. 4 is a schematic for illustrating a construction in which the power-off circuit is provided in each slot of the DE. As shown in FIG. 4, because power-off circuits 50 to 65 are connected to each slot of a DE 40, even if a malfunction occurs in a specific HDD, the corresponding power-off circuit can block power supply only to the malfunctioning HDD, thereby enabling to prevent the shutdown of the entire DE 40.
For example, if a malfunction occurs in an HDD 3, a power-off circuit 53 blocks the power supply to the HDD 3, retaining the power supply to other HDDs, thereby preventing shutdown of the entire DE 40.
In a technology disclosed in Japanese Patent Application Laid-Open No. 2005-190052, a plurality of HDDs included in a motherboard is mounted on a chassis and a single high voltage is supplied to each chassis, thereby enabling to mount multiple types of HDDs on the motherboard.
However, as shown in FIG. 4, connecting the power-off circuit to each slot of the DE 40 results in a waste of a large number of power-off circuits. This is because the number of HDDs that are mounted inside the DE varies according to structure of the device, and the number of the HDDs may be smaller than the number of the slots. In the example shown in FIG. 4, since the DE 40 includes only HDDs 0 to 5, power-off circuits 56 to 65 are wasted.
The power supply to each HDD can also be controlled by incorporating a power-off circuit for each HDD into the power supply unit. However, this increases size and complexity of the power supply unit, thereby increasing cost.